Cure temperature influences composite electrical properties by carbon nanotube-rich domain formation

Abstract

Carbon nanotube (CNT) nanocomposites are enticing materials that enable engineers to tailor structural and electrical properties for applications in the automotive and aerospace industries. CNT mass fraction and the matrix cure temperature are two ways to tune the direct and alternating current electrical properties of these nanocomposites; yet, how mass fraction and cure temperature affect electrical properties remains unclear. In many cases, nanofillers such as carbon nanotubes appear in concentrated domains within the nanocomposite. Recent insights into nanoparticle-rich domain formation and its influence on electrical properties raise questions about which processing variables might optimally tune a material's functionality. Utilizing recently developed, nondestructive measurement techniques such as scanning lithium ion microscopy and microwave cavity perturbation spectroscopy, new insights are presented into the role of mass fraction and cure temperature in multiwall carbon nanotube – bisphenol A diglycidyl ether epoxy composites. Here, it is found that both mass fraction and cure temperature affect the electrical properties. Specifically, beyond the electrical percolation threshold, the DC conductivity is an order of magnitude higher for composites prepared at elevated cure temperatures for a given CNT mass fraction. Direct observations of the microdomain morphology do not show substantial differences due to cure temperature. These findings suggest pathways to generate designer nanocomposites for advanced electrically-active applications.